Bettas -- particularly males -- tend to be aggressive toward other bettas and cannot be housed together. However, you can quickly turn your betta tank into an aquarium for two or more fish by dividing it into smaller sections.
Step 1
Ensure your betta tank is sufficiently large to divide. Each fish should have, at minimum, one gallon of water, so small vases and containers can't be divided.
Step 2
Remove the fish and water from the tank and place them in a separate tank or bucket. Dry the sides of the aquarium with an absorbent towel.
Step 3
Apply the slide on bars that came with the tank divider to the side of each tank. They should be long enough to run top to bottom of the tank. Then insert the plastic divider into the slide on bars. Test it to ensure the fish cannot knock through it, then refill the water and place the fish in the divided tank.
